Pistons



Feb. 19, 1957 A, 1 HEWSQN 2,782,083

PISTONS Filed Aug. 2. 1954 United States Patent O f' PISTONS Andrew James Hewson, Merlynston, Victoria, Australia Application August 2, 1954, Serial No. 447,135V

2 Claims. (Cl. 309-14) This invention relates to pistons, more particularly to pistons for internal combustion engines.

Pistons of the kind to which this invention relates are provided with circumferential grooves around their outer surfaces to accommodate metal rings, and when replacing worn or damaged rings with new ones, it has hitherto been necessary to remove each piston entirely from the cylinder block in order to accomplish the removal and replacement of the piston rings.

The operation of renewing the rings on the pistons of a standard internal combustion engine, in accordance with present practice, involves the removal of the pistons from the cylinders, to do which it is necessary iirstly to remove the engine sump or the crank casing and secondly to remove the engine connecting rods, big-end bearings from the engine crank-shaft journals.

It is further necessary, to enable accurate litting of the piston rings that the engine cylinder head be removed, and, in all, the operation of renewing the piston rings on the pistons of an internal combustion engine, is a lengthy, tedious and costly process.

The principal object of this invention is to provide a piston so constructed as to render unnecessary the wholesale dismantling of engine parts when renewing the piston rlngs.

-Another object of the invention is to provide a piston from which the rings may be removed, and on which they may be replaced in a simple and expeditious manner.

By the use of this invention, in removing and replacing piston rings on the pistons of internal combustion engines, it is necessary only to remove the engine cylinder head, in order to enable the operation to be performed.

A piston constructed in accordance with this invention, comprises a lower part of normal construction to a point immediately above the internal bosses, which receive the gudgeon pins, an upper part reduced in diameter and externally screw-threaded, a removable ring-carrying body adapted for screw-threaded engagement with the said upper part, means to lock the ring-carrying body to the upper part to prevent accidental displacement thereof, and tool-receiving depressions in the top face of the ring-engaging member to enable the ring-carrying member to be rotated relatively to the said top part of the piston, for removal and/ or replacement.

Reference is directed to the accompanying drawings, wherein:

Figure 1 is an exploded, cross-sectional elevation of the piston.

Figure 2 is a cross-sectional elevation showing the parts in assembled and locked position.

Figure 3 is a plan view.

In carrying the invention into practical effect, there is provided a piston having a normal lower part 4 and internal, hollow bosses 5. Above the bosses 5 the piston is reduced in diameter to provide an upper part 6 having the external screw thread 7 and an internally screw threaded hole 8, which terminates in a thickened part 9 on the top wall 10.

The piston rings 11, fitted into normal circumferential grooves 12, are carried by a hollow body 13 which is provided with an internal screw thread 14 which is complementary to the screw thread on the external wall of the said reduced part of the piston.

The top wall 15 of the body 13 is provided with the counter-sunk bore 16. A countersunk machine screw 16 2,782,083 Patented Feb. 19, 1957 ICC is arranged to pass through the bore 16, into the threaded hole 8 in the top wall 10 of the reduced part of the piston, whereby the two parts may be secured together.

A locking member 17 is provided, adapted to t under the head of the screw 16a, and the locking member has a tail arranged to locate in a tool-receiving hole 18 of which thereare two provided at diametrically opposite sides of the top wall 15.

A tool, such as a suitable Spanner, has a pin adapted to enter the holes 18 to enable the ring-carrying member to be tightened on the upper part of the piston, or be removed therefrom.

When it is required to attend to the piston rings, the engine cylinder head is removed. The piston to be worked on is brought to its highest point, after which the screw 16a is removed, together with the locking member 17. Thereafter the Spanner or removing tool is employed to loosen the ring-carrying body from the upper part of the piston, and after being started the ring-carrying body may be removed by hand.

The old rings may then be removed, replaced by new ones, and the ring-carrying member is then screwed back on to the cylinder, and locked in place.

I claim:

l. A piston having a lower portion provided with hollow bosses therein, said piston being reduced in diameter above the bosses to provide an upper portion having an external screw-threaded recess, said recess being formed in the top wall of said upper portion and terminating in a thickened portion of the top wall, a hollow body adapted to fit on said upper portion and having an internal screw thread which is complementary to the external screw thread on said upper portion, said hollow body being provided with circumferential grooves around its outer surface adapted to receive piston rings, the top wall of said hollow body being provided with a countersunk bore adapted to be aligned with the screw-threaded recess in the top wall of said upper portion of the piston, said bore and said recess being adapted to receive a countersunk machine screw for securing said hollow body to said upper portion, said top wall of said hollow body being provided with tool-receiving holes at diametrically opposite sides thereof for reception of a tool for removing said hollow body from said upper portion, and a locking member comprising a portion adapted to lie under the head of said machine screw, and a tail adapted to engage in one of the tool-receiving holes.

2. A piston having a lower portion provided with hollow bosses therein, said piston being reduced in diameter above the bosses to provide an upper portion having an external screw thread, a removable ring-carrying body adapted for screw-threaded engagement with said upper portion, said ring-carrying body being provided with tool-receiving depressions in its top face for reception of a tool to permit the ring-carrying body to be rotated relatively to said top portion, said body and said upper portion being provided with aligned screw-receiving means, and means to lock the ring-carrying body to the upper portion to prevent accidental displacement thereof, said last-named means comprising a screw engageable in said aligned screw-receiving means, and a locking member having a portion adapted to lie under the head of said screw, and a tail adapted to be received in one of said tool-receiving depressions.

References Cited in the le of this patent UNITED STATES PATENTS 1,368,938 Kecskemety Feb. 15, 1921 FOREIGN PATENTS 862,930 France Mar. 19, 1941 463,260 Canada Feb. 21, 1950 

